Malleable suture fasteners such as the sleeves sold under the trademarks Ti-KNOT® and COR-KNOT® by LSI Solutions, Inc. are a significant improvement over hand or instrument-tied knots in laparoscopic surgical procedures. The sleeves, which are made of a malleable material that has proven safe with prolonged exposure to body tissue, are slid over two or more strands of suture and deformed or crimped to secure the strands of suture.
An exemplary crimping instrument is shown in U.S. Pat. No. 7,235,086, entitled “CRIMPING INSTRUMENT WITH MOTION LIMITING FEATURE”, assigned to LSI Solutions, Inc., of Victor, N.Y. FIG. 1 illustrates such a crimping device 20, having a handle 22 with an actuator 24 that is movable relative to the handle 22. A hollow shaft 26 extends from the handle 22 to a distal end 28 of the shaft 26. The distal end 28 of the shaft 26 can be seen more clearly in the partial cross-sectional view of FIG. 1A.
Suture ends 30 can be threaded through a crimping sleeve 32 held between a hammer 34 and an anvil 36. The suture ends 30 pass out a hole in the side of the shaft 26, and the device can be used to position the crimping sleeve 32 at a desired location on the suture 31 relative to a surface 38 through which the suture 31 has been secured (for example, tissue, a replacement anatomical structure such as a heart valve, or an augmentive anatomical structure such as a heart valve annulus).
Squeezing the actuator 24 towards the handle 22 causes a wedge 40, located in the shaft 26, to advance and to force the hammer 34 into the crimping sleeve 32. The hammer 34 crimps the crimping sleeve 32 against the anvil 36, and the suture 31 is held tightly by the deformed sleeve 32. A blade 42 may also be incorporated within the shaft 26 and can be simultaneously moveable by the actuator 24 in order to trim the suture ends 30.
Such instruments for attaching suture fasteners 32 have proven to be very effective. The Ti-KNOT® and COR-KNOT® devices from LSI Solutions, Inc. (information available at www.lsisolutions.com) have been widely accepted by surgeons for the recognized benefits of time savings, ease of use, and reliability. (See, for example, “New Knot Tying Technique for Minimally Invasive Approach to Mitral Valve Repair”, an abstract by Rodriguez, Sutter, and Ferdinand presented at the AATS 2011 Mitral Conclave in New York, N.Y. in 2011 or “Use of Automatic Knot-Tying and Cutting Device is Shortening Aortic Cross-Clamp Times in Minimally Invasive Mitral Valve Surgery”, an abstract by Gersak and Robic presented at the 26th Annual EACTS Meeting in Barcelona, Spain in 2012.)
Devices like the COR-KNOT® device enable many types of minimally invasive surgery (MIS), or, more specifically, minimally invasive cardiac surgery (MICS). MIS is a type of surgery performed through one or more small incisions or access sites created in a patient. MIS has been shown to have at least equivalent morbidity and mortality outcomes as compared to conventional approaches, with reported advantages of reduced postsurgical pain, better respiratory function, shorter hospital stay, and improved cosmesis. Such advantages are increased with ever smaller sized MIS access points. As a result, it is very desirable to have smaller and smaller MIS tools which can enable the use of such smaller MIS access points. In other MIS approaches, specifically, for example MICS for aortic valve replacement, a smaller device tip, especially with more rounded edges, would be easier to position remotely and would reduce the potential for device-related tissue trauma and/or prosthetic damage.
The outside of the prosthetic valve shall be close in size to the space available at the aortic root. The larger a replacement aortic valve's blood passage area is relative to the opening in the outflow track of the left ventricle, the more blood can pass through without flow disturbances. After removing the diseased native valve, it is therefore desirable to install a replacement prosthetic valve with the largest possible diameter into the aortic root. Replacement heart valves usually have a sewing ring attached to and just peripheral to the valve leaflet. This ring is typically several millimeters wide, is designed to be sutured to the aortic root, and can then be secured in place with mechanical knots. Given the narrow space available over the sewing ring between the valve leaflets and the aortic root, a mechanical knot delivery device about the same size as the radial width of a sewing ring is desired. A narrower MICS device tip would enable less challenging placement of the mechanical knot into this narrow space as well as easier device tip positioning and removal. A narrow device tip can also enable the use of larger diameter valves for improved blood flow.
Unfortunately, it is not a simple matter to reduce the size of all of the components in a device such as the current COR-KNOT® device because such changes could also impact the size (and therefore the operating properties) of the mechanical crimping sleeve 32. Devices such as the COR-KNOT® device are always put through rigorous testing and qualification procedures, both internally with the manufacturer and externally, such as when obtaining Food and Drug Administration (FDA) and European Community (CE mark)clearance. Currently, the outside diameter of the COR-KNOT® device shaft 26 is approximately two-hundred thousandths of an inch. The inside diameter of the shaft 26 is approximately one hundred seventy-six thousandths of an inch, while the titanium sleeve 32 has an outside diameter of approximately forty-nine thousandths of an inch. Subtracting the room needed for the sleeve 32 within the shaft 26, this means that the current COR-KNOT® device only has about one hundred twenty-seven thousandths of an inch to accommodate the hammer 34, anvil 36, travel space for the wedge 40, and various associated tolerances. Reducing the size of the crimpable sleeve to gain more room in a smaller shaft could potentially require a different size crimpable sleeve. The current sleeve has been very successfully used in over 250,000 patients throughout the world. This sleeve size has proven completely reliable and useful with a broad range of common surgical sutures; no failures have been reported after securing over 1.8 million sutures. This sleeve size is remarkably effective and well-received; changing its dimensions or configuration would have the potential to render it less efficacious. Likewise, it would be unwise to change the operating features of the hammer 34 and anvil 36 which impart the reliable crimped configuration for the proven suture sleeve 32. Still, it would be desirable to have a crimping device 20 with smaller shaft 26 dimensions in order to enable use with ever smaller MIS access points and in MICS applications.
Therefore, there is a need for a surgical crimping instrument having smaller dimensions when compared to the currently available devices, which are already quite small. Furthermore, there is a need for such a reduced dimension surgical crimping instrument to have continued compatibility with existing uncrimped sleeves for loading and crimping them to an identical configuration to ensure the continuation of reliability and performance from such proven sleeves. Finally, there is a need for such devices to place a premium on patient safety, so it would also be desirable for this surgical crimping instrument to have even further enhanced tissue protection features.